Think Zero Dark Thirty is a gung-ho actioner then think again. Brave Two Zero it’s not. Kathryn Bigelow’s labyrinthine film is a forensic account of the ten year search for Osama bin Laden. Taut and unsparing, it’s a head-reeling two-hour-forty minutes of pure concentration.

In the aftermath of 9/11, Black Ops CIA operatives are getting down and dirty, torturing a terrorist. One of the bystanders is Maya (Jessica Chastain) a young CIA agent new to the water-board world of information extraction. They’re after bin Laden. And Maya’s queasy entrée to the flint-edged world of counter-terrorism hardens over time as the clues stack up or go nowhere. London…Islamabad, the outrages continue. Bit by bit, the end is coming, zeroing in on bin Laden’s hideout.

Bigelow’s Hurt Locker was the surprise Oscar-winner of 2010. And Zero Dark Thirty has a similarly pared-down, unsentimental, documentary edge. No point-making, flag-waving, boot-on-ground heroics here. Bigelow excels at cutting away just when you sense that other film-makers would pump us up or soothe us down.

Intelligently scripted, Zero Dark Thirty takes no prisoners - at least not with its audience. Reach for your popcorn and you’re out of the loop. Names and plans come at you with bewildering speed. And Bigelow charts the passing of time, and gives you pause for thought, with inter-titles, chopping the film into Parts.

Jessica Chastain (The Help, Tree of Life) is our eyes throughout the film. It’s a clever, low key perspective, leaving out any backstory or emotional baggage and focusing solely on the search. But Chastain’s conversion from ingénue to hard-ass isn’t convincing. As a catalyst for action, she’s not ultra-believable. But her struggle for permission to hit bin Laden is edgily done.

A smattering of cameos – Jennifer Ehle (BBC’s Pride and Prejudice), Mark Strong (Tinker Tailor, Body of Lies), even John Barrowman (Torchwood) – adds to the sense of complexity and passing time. But most are talking heads. Only occasionally does action intrude into the film – notably the Marriott Hotel bomb attack in Pakistan, a tense covert-meeting-gone-wrong and the climactic 40 minute Navy SEAL assault.

Bigelow wisely acknowledges global sensitivity by depicting the assault in a forensic manner, with no camera-shots of Bin Laden, alive or dead. True to its guns, Zero Dark Thirty sees it from the technicians’ point of view. As with The Hurt Locker, the emotional payout is quiet and unspoken. And the film ends with an arresting, absolutely note-perfect image.

Starkly shot, with a sometimes wobbly camera, it’s a long-haul film that pitches you straight into the sweat and graft of counter-terrorism. Unlike 24, it’s not an adventure. Unlike Syriana it does make sense. A thriller yes but it doesn’t play ball. American navel-gazing perhaps. But thoughtfully, calmly and with some very long words.

Amidst all this stands CIA Agent Maya (an Oscar-nominated Jessica Chastain), who is drafted into the US Embassy in Pakistan a couple of years after the events of September 11th, 2001. But before she has even been allocated a desk, she is at a 'black site' with fellow agent Dan (Jason Clarke) observing a torture session. Over the following years, it is she who spearheads the continual search, right through to its conclusion. She oversees the torture of more than one individual, and becomes obsessed with the idea that a mysterious man named Abu Ahmed is key to locating the al-Qaeda leader. Ultimately, it is her unremitting pursuit and pressurising of her superiors that lead to raid on the compound in Abbottabad, where "UBL" was finally found.

The opening half the film deals in the gathering of information and, amidst the torture and terrorism, a lot of it is thrown at the audience. There is seldom anything provided in the way of context but, in general, the script doesn't leave anyone behind. Maya is sidelined somewhat as the focus naturally shifts to the extensive raid sequence and, although the final hour is absolutely riveting stuff, the balance of the overall piece suffers a little because of it.